<p>As far as the Physics is concerned, you don't have to go quite as deep into fluids/thermo as an ME and you don't have to go quite as deep into electromagnetism as a EE. However, whereas ME's generally do not take an electromagnetics course beyond Physics II and EE's generally don't take a fluids course - you will take it all. This is in addition to your biology and chemistry courses (which generally neither ME's or EE's take beyond an introductory level, if that).</p>
<p>I would say the "hardest" engineering major greatly depends on the college (I do not know anything about UPenn Engineering). But I imagine, in most cases, Biomed is up there with ME and EE.</p>
<p>EDIT: By the way, Industrial Engineering (IE) is generally acknowledged as the easiest engineering major. It definitely involves the least amount of Physics and supposedly has synergy with a Business degree.</p>